Is there any way to get rid of too many polygons in mesh?
There are two main ways that I know of:


Using the Decimate modifier. It combines near faces that are similar.
Un-subdivide works for me, but you could also use collapse or planar depending on your situations. On Unsubdivide, more iteration means less faces.





You could also do a manual re-topology. That's where you go through and manually combine faces.
I'm not a master at this, so I can't tell you much, but I'm sure there are some great tutorials online about it.